USB: xhci: Set EP0 dequeue ptr after reset of configured device.

When a configured device is reset, the control endpoint's ring is reused.
If control transfers to the device were issued before the device is reset,
the dequeue pointer will be somewhere in the middle of the ring.  If the
device is then issued an address with the set address command, the xHCI
driver must provide a valid input context for control endpoint zero.

The original code would give the hardware the original input context,
which had a dequeue pointer set to the top of the ring.  This would cause
the host to re-execute any control transfers until it reached the ring's
enqueue pointer.  When issuing a set address command for a device that has
just been configured and then reset, use the control endpoint's enqueue
pointer as the hardware's dequeue pointer.

Assumption:  All control transfers will be completed or cancelled before
the set address command is issued to the device.  If there are any
outstanding control transfers, this code will not work.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/xhci-mem.c

@@ -835,6 +835,27 @@ int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
 	return 0;
 }
 
+void xhci_copy_ep0_dequeue_into_input_ctx(struct xhci_hcd *xhci,
+		struct usb_device *udev)
+{
+	struct xhci_virt_device *virt_dev;
+	struct xhci_ep_ctx	*ep0_ctx;
+	struct xhci_ring	*ep_ring;
+
+	virt_dev = xhci->devs[udev->slot_id];
+	ep0_ctx = xhci_get_ep_ctx(xhci, virt_dev->in_ctx, 0);
+	ep_ring = virt_dev->eps[0].ring;
+	/*
+	 * FIXME we don't keep track of the dequeue pointer very well after a
+	 * Set TR dequeue pointer, so we're setting the dequeue pointer of the
+	 * host to our enqueue pointer.  This should only be called after a
+	 * configured device has reset, so all control transfers should have
+	 * been completed or cancelled before the reset.
+	 */
+	ep0_ctx->deq = xhci_trb_virt_to_dma(ep_ring->enq_seg, ep_ring->enqueue);
+	ep0_ctx->deq |= ep_ring->cycle_state;
+}
+
 /* Setup an xHCI virtual device for a Set Address command */
 int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *udev)
 {

drivers/usb/host/xhci.c

@@ -2134,6 +2134,8 @@ int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
 	/* If this is a Set Address to an unconfigured device, setup ep 0 */
 	if (!udev->config)
 		xhci_setup_addressable_virt_dev(xhci, udev);
+	else
+		xhci_copy_ep0_dequeue_into_input_ctx(xhci, udev);
 	/* Otherwise, assume the core has the device configured how it wants */
 	xhci_dbg(xhci, "Slot ID %d Input Context:\n", udev->slot_id);
 	xhci_dbg_ctx(xhci, virt_dev->in_ctx, 2);

drivers/usb/host/xhci.h

@@ -1292,6 +1292,8 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags);
 void xhci_free_virt_device(struct xhci_hcd *xhci, int slot_id);
 int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id, struct usb_device *udev, gfp_t flags);
 int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *udev);
+void xhci_copy_ep0_dequeue_into_input_ctx(struct xhci_hcd *xhci,
+		struct usb_device *udev);
 unsigned int xhci_get_endpoint_index(struct usb_endpoint_descriptor *desc);
 unsigned int xhci_get_endpoint_flag(struct usb_endpoint_descriptor *desc);
 unsigned int xhci_get_endpoint_flag_from_index(unsigned int ep_index);